In this research, a manual milling machine was retrofited to the NC milling system economically. This NC milling system was composed of DC servomotor, ballscrew, coupling, interpolation board, motor controller, personal computer and etc. It has two dimensional NC milling ability and is controlled by PC. For the improvement of NC milling system's position error, the compensation is applied.
At the milling process, abnormal machining states, such as tool fracture, chatter and excessive cutting force might oacurre. This state can be prevented by cutting force control. For the control of cutting force, spindle motor current was measured since it is proportional to the cutting force and feedrate is adjusted for maintaining the cutting force constant.
